Method and system for agricultural fertigation

ABSTRACT

An agricultural fertigation method includes the continuous introduction of concentrated raw materials into a high-dilution irrigation-water environment whereby the stream of flowing irrigation water dampens the resultant dissolution and reaction exotherms. A system wherein raw materials are efficiently continuously fed to the irrigation system main line or a side-arm reactor efficiently implements the method.

This application is a continuation in part of co-pending application Ser. No. 13/136,032, filed on Jul. 21, 2011, which is a continuation in part of application Ser. No. 12/283,448, filed on Sep. 12, 2008, claiming the domestic priority benefit of application No. 61/056,151 filed on May 27, 2008, inventors Miller et al.

BACKGROUND OF THE INVENTION

The present invention relates to methods for adding fertilizer nutrients, particularly potassium, to agricultural irrigation systems, including particularly agricultural micro-irrigation and sprinkler systems.

The agriculture industry adds fertilizers to the plant environs, such as the soil, to enhance crop growth and subsequent yields. Commercial fertilizers are usually selected of a variety of formulations depending on the crop and its nutrient requirements.

Fertilizers generally are classified according to their NPK content. NPK is common terminology used in the fertilizer industry and stands for: (1) N—the amount of nitrogen in the formulation as N; (2) P—the amount of phosphorus in the formulation as P₂O₅; and (3) K—the amount of potassium in the formulation as K₂O. Nitrogen, phosphorus and potassium are the basic plant nutrients or macronutrients that are taken up and utilized by the growing crops, and that are provided by the addition of fertilizers (NPK fertilizers).

A fertilizer, as that term is used herein and as generally understood, refers to the nutrient-containing materials used to deliver fertilizer nutrients to a crop. Conventional fertilizers typically will contain materials that are extraneous to the crop's nutrient-uptake (“nutrient-extraneous materials”) but which, for practical and/or other reasons, are necessary to the delivery of the nutrients. The process of delivering fertilizer nutrients to crops is referred to as fertilization.

The fertilization method of adding fertilizers to the water being used to irrigate the crops is called “fertigation”, reflecting this combination of irrigation and fertilization. Fertigation reduces the labor expended in the addition of fertilizers.

To conserve water, which is decreasing in availability and increasing in cost, current conventional technology includes micro-irrigation systems that deliver precise amounts of water directly to the soil holding the root system of the plant that is being grown. In the past twenty to thirty years, a large percentage of crop producers in the western and southwestern United States have converted from flood and sprinkler irrigation systems to micro-irrigation technology. Micro-irrigation systems contain devices called emitters, micro-sprinklers or other such devices that provide the precise amounts of water directly to the desired soil site, namely the soil holding the roots of the plant or crop being irrigated. Upon conversion to micro-irrigation systems, farmers began adding fertilizers through them.

Micro-irrigation systems, unfortunately, are sensitive to water quality and the inclusion of fertilizers and other additives. The sensitivity of micro-irrigation systems to water quality and additives stems from the refinement of the micro components in a micro-irrigation system. These emitters, micro-sprinklers or other micro devices deliver the desired precise amounts of water so long as they do not plug or foul. Plugging occurs when deposits, from any source, build up inside these devices. The smallest particle or foreign material can cause fouling of these devices because these devices have very tiny orifices and/or a long tortuous narrow passageway that provide the requisite pressure for delivery of precise amounts of water in a uniform manner to each plant in the crop being irrigated. Water quality and the inclusion of fertilizers can, and frequently does, cause severe plugging problems. The problems arise from a number of factors: (1) the irrigation water is typically obtained from wells, reservoirs, canals, lakes, or rivers which contain various amounts of dissolved minerals; and (2) fertilizers can form insoluble salts and/or cause particulate formation when added to the water. Macro-irrigation systems mainly tolerate these conditions, while micro-irrigation systems are extremely intolerant.

In more detail, the addition of fertilizer formulations to the micro-irrigation water increases the loading of inorganic salts over that already in the water. When the loading, or the combined loading, is too high, the solubilities of at least some of the naturally-occurring minerals and/or added compounds are exceeded and particulate formation increases dramatically. When particulates form, significant deposits begin to build up throughout the entire micro-irrigation system. The end result is plugging of the emitters or micro-sprinklers.

Plugging results in uneven distribution of water and nutrients to the crop being irrigated. In some cases, complete shut-down of the irrigation system occurs. Therefore problem-free use of additives such as fertilizers in micro-irrigation systems is normally seen only in irrigation systems that use relatively pure water sources.

The conventional agricultural practice is to make intermittent or periodic applications of fertilizers. Such intermittent additions might be a single addition, or a plurality of additions, of large amounts (high concentrations) of fertilizer during a brief time interval each growing season or crop cycle. (The number of applications per growing season or crop cycle usually depends on the crop and/or the type of fertilizer being added.) When the fertilizer-delivery method is fertigation, fertilizers are typically slug fed into the irrigation system as quickly as possible to minimize the labor requirements and ease material handling. Slug feeding of a block (portion of a field) normally entails feeding the large amounts (high concentrations) of fertilizer to the irrigation water over a six to seven hour period during irrigation, and then, after the fertilizer feed is shut off, continuing the irrigation of that block for an additional two to three hours to rinse out all of the fertilizer that is contained inside the irrigation system, insuring that all of the fertilizer intended for the block is in fact delivered to the block. Fertigation reduces equipment, fuel and labor costs in comparison to mechanical delivery of fertilizers to the crop, and thus fertigation achieves a significant overall cost savings.

The cost of commercial fertilizer formulations is, however, itself significant, and commercially viable fertilizer formulations (formulations sufficiently inexpensive for bulk agricultural use) typically include, as mentioned above, nutrient-extraneous materials which do not contribute to plant nutrition, and can even be undesirable components.

The term “micro-irrigation” as used herein and in the claims refers to microsprinkers, drip, and subsurface drip systems.

SUMMARY OF THE INVENTION

The present invention provides a method and/or system for fertigation wherein a potassium-nutrient feedstock (two or more raw materials or inputs) is charged to an active irrigation system continuously, or substantially continuously, at very low levels, during the entire time, or substantially the entire time, that irrigation water is sufficiently flowing through the irrigation system via a system that provides a high-dilution environment in the feedstock-component intermixing zone. The present method provides on-site fertilizer formulation from the feedstock as that feedstock is charged to the irrigation system continuously, or substantially continuously, at very low levels, during the entire time, or substantially the entire time, that irrigation water is sufficiently flowing through the irrigation system, whereby a potassium-nutrient feedstock is formulated that has a higher potassium-nutrient content, has low or minimal nutrient-extraneous material, contains no degradable thiosulfate and is drastically less costly because basic commodity raw materials are used, which are advantages that are not available from conventional commercial fertilizers or practices. The feedstock is comprised of potassium hydroxide and at least one mineral acid that intermix as the feedstock is charged to the irrigation system. In preferred embodiments, the system of the present invention is automatic and subject to variation of the amount and type of raw materials forming the feedstock as desired.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an at least partially diagrammatic view of a system of the present invention.

FIG. 2 is an at least partially diagrammatic view of a section of the system of FIG. 1.

FIG. 3 is an at least partially diagrammatic view of a section of the system of FIG. 1.

FIG. 4 is an at least partially diagrammatic view of a section of a system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

On-Site, In-Situ Fertilizer Formulation

The method and/or system of the present invention, namely the method and/or system for fertigation by charging a potassium-nutrient feedstock, rather than a commercial fertilizer to the irrigation system, is drastically less costly because basic commodity raw materials are used, which is an advantage that is not available from conventional commercial fertilizers or practices. The feedstock is comprised of potassium hydroxide and a mineral acid, such as sulfuric acid for example, or nitric or phosphoric acid, that intermix as the feedstock is charged to the irrigation system. At the preferred concentrated levels of potassium hydroxide and mineral acid, the feedstock is a 0-0-42 NPK fertilizer. Conventional agricultural practices would never mix potassium hydroxide and mineral acid on site because doing so in even small quantities would create an explosion. The most basic (simple) sources of potassium used in conventional agricultural fertigation are potassium sulfate and potassium thiosulfate. Potassium sulfate is soluble only up to 8% potassium as K2O (a 0-0-8 NPK fertilizer), requiring huge costs for (a) the shipment and storage of this dilute fertilizer and (b) the time and labor required to slug-feed such a dilute material to an irrigation system. Potassium thiosulfate (a 0-0-25 NPK fertilizer) has a higher solubility than potassium sulfate (but still far lower than the present invention's 0-0-42 NPK feedstock) but it is expensive and, since the sulfur of thiosulfate is not in its highest oxidation state, it is at risk of decomposition and precipitation, which leads to fouling of the irrigation system. (No oxidants, such as chlorine, can be used in the irrigation system at or about the same time as potassium thiosulfate.) Potassium nitrate, another potassium source, is very soluble but is not used in conventional agricultural practices because (a) its distribution is restricted or prohibited by laws and/or regulations because of security risks associated with its nitrate content and (b) it is prohibitively expensive. Potassium phosphate, another highly soluble potassium source, is also much too expensive for conventional fertigation practices and the phosphate can cause precipitation and fouling problems. As to the mineral acid, while sulfuric acid is the preferred mineral acid used in the present system and method, leading to the in-situ formation of potassium sulfate (without the detriments associated with conventional potassium sulfate solutions), the use of nitric acid or phosphoric acid leads to the in-situ formation of potassium nitrate and potassium phosphate respectively. The charge of a nutrient feedstock to the irrigation system continuously or substantially continuously at very low levels also provides a uniform, consistent level of nutrient availability throughout a crop cycle, in comparison to conventional fertigation techniques, as discussed below.

As discussed above, the potassium-nutrient feedstock used in the present invention is a combination of potassium hydroxide and a mineral acid. The preferred mineral acid is sulfuric acid, although in broad embodiments other mineral acids, such as nitric and phosphoric acids, and combinations of mineral acids, are not excluded. These basic raw materials cannot be added to an irrigation system using conventional practices. The present invention does not exclude the concomitant addition of other materials if desired, including but not limited to one or more other fertilizers and the like.

Potassium Hydroxide

Potassium hydroxide is never used in agriculture due to its caustic nature which results in safety and handling problems for the grower. In addition, severe plugging problems in the irrigation system would be the major problem because, even under extremely dilute conditions, enough alkalinity would be present to cause severe calcium and/or magnesium carbonate precipitation leading to a disastrous plugging of the irrigation system. Further, if the high alkalinity of potassium hydroxide did make it through the irrigation system without plugging it totally, the alkalinity remaining in the water would cause severe “hardpanning” (forming a rock hard bather that water cannot penetrate) upon interaction with the soil. Additionally, the high alkalinity of potassium hydroxide would also be very toxic to the crop.

Mineral Acids—Sulfuric, Nitric and Phosphoric Acid

Concentrated mineral acids; including sulfuric, nitric and phosphoric acids, are very corrosive materials that necessitate special equipment and safety precautions and the addition of any of these acids under conventional practices creates a risk of (a) corrosion of the metal components of the irrigation system and (b) embrittlement of, and damage to, the sensitive plastic irrigation-system components (emitters and the like) that deliver regulated amounts of water to each plant.

Conventional Fertigation Methods and the Unbalanced Nutrient Availability Drawback

As discussed above, the conventional method of fertilizer addition, by conventional fertigation or mechanical means, involves adding the fertilizer about once or twice a growing season or crop cycle because of the logistics and labor that are required. When the fertilizer is accordingly slug fed to the field, it is typically fed at a very high rate over a short period of time, whereby a high concentration of fertilizer is added to the root zone of the crop. This high concentration of fertilizer is greater than the plant can absorb, and therefore it is not completely absorbed (which is why a portion of it is considered one of the “nutrient-extraneous materials”). Some of the residual fertilizer, which typically is a high fertilizer residual, interacts with the soil. These fertilizer-soil interactions normally result in the formation of insoluble inorganic salts, with a concomitant and substantially irreversible loss of available fertilizer. Further, each subsequent non-fertigation irrigation drives or washes available residual fertilizer away from the wetted root zone core towards the perimeter of the wetted zone, mechanically diminishing its availability to the plant. Eventually, the fertilizer concentration gradient which is created results in very little fertilizer being available within the wetted root zone. The level of available residual fertilizer in the wetted root zone will typically drop to essentially zero for a time period ahead of the next fertigation. For these reasons, conventional fertigation practices lead to huge swings in the amount of fertilizer that is available to the plant over time. These swings in available fertilizer in turn lead to costly compensations in the form of increased fertilizer feeds. In other words, the amount of fertilizer that is considered required is increased because a significant portion of the residual fertilizer becomes unavailable to the plant.

The Basics of the Present Fertigation Method and System

The potassium-nutrient feedstock is charged to an irrigation system by concomitantly feeding its components (raw materials) to a water stream (preferably a stream of irrigation water) either (1) flowing through a mixing chamber that discharges to a main line of an irrigation system downstream of any irrigation-system filters and upstream of the delivery points of the irrigation system or (2) flowing through a main line of an irrigation system (that is, directly charging to a main line of an irrigation system) downstream of any irrigation-system filters and upstream of the delivery points of the irrigation system. The intermixing of components therefore is initiated either in a mixing chamber upstream of the irrigation system's main line or within the main line itself.

The present method and system of the present invention preferably employ an automated feed system which simultaneously feeds or charges the plurality of raw materials to the mixing chamber or main line at a pre-selected or pre-determined rate. Such an automated feed system therefore charges a potassium-nutrient feedstock of a pre-selected or predetermined composition at a pre-selected or pre-determined rate. The automatic feeding of the potassium-nutrient feedstock at a pre-selected or pre-determined rate is particularly important when it is desirable to feed the feedstock at a rate relative to the irrigation-water flow rate, so as to automatically provide and maintain a pre-selected or pre-determined concentration of each potassium-nutrient raw material in the irrigation water throughout the fertigation period, including when the irrigation water flow rate varies from one set to the next. Such an automated feed system would be inactive or idle when there is no irrigation water flow in the irrigation line served by the automated feed system. That automated feed system may be, and in certain embodiments is preferably, automatically activated or triggered upon the commencement of water flow in the irrigation line, and may be, and in certain embodiments is preferably, automatically deactivated or halted when the flow of irrigation water ceases.

The charge of the potassium-nutrient feedstock to the irrigation water is at a very low level feed so as to restrict or confine potassium-nutrient-feedstock concentration in the irrigation water to very low levels at all times. The charge of the potassium-nutrient feedstock to the irrigation water is continuous. By a continuous charge (or continuously charging) of potassium-nutrient feedstock is meant herein that the charge is continuous when irrigation water is sufficiently flowing to dampen the exotherm that results from the charge, or in other words, substantially continuous throughout the irrigation cycles or continuous when the irrigation system is active. In more detail, when an irrigation system is idled, water usually drains out and the system becomes mainly filled with air. Upon reactivation, there is a time delay between the start of water flowing into the irrigation system and the point of time at which the system reaches its full or normal operating pressure (from about 10 to 150 psi depending on the system). The continuous charge of potassium-nutrient feedstock ceases when the shut down (the idling) of the irrigation system initiates (and the water pressure falls below full or normal operating pressure for the given system) and does not recommence until at least a preponderance of the irrigation system is refilled with water, at which point the system is typically approaching, but might not yet be at, its full or normal operating pressure. The water-flow characteristics required to dampen the exotherm can be calculated using simple thermodynamics for any given irrigation system. An alternative determinant is ninety percent of full or normal operating pressure, or in other words, by a continuous charge of potassium-nutrient feedstock is meant herein that the charge is continuous (although it can vary as to selection of raw materials) throughout a crop cycle when irrigation water is flowing at least at ninety percent of full or normal operating pressure.

The Present Fertigation Method and Alleviation of the Unbalanced Nutrient Availability Drawback

In contrast to huge swings in available fertilizer when the fertilizer is slug fed about once or twice during a crop cycle, in the present method the potassium-nutrient feedstock is added continuously at a very low level. Therefore the level of available fertilizer in the wetted root zone will remain substantially uniform over the entire crop cycle. There will be no swings in the amount of fertilizer that is available to the plant over time. There will be no lost-fertilizer compensations in the form of increased fertilizer feeds. The amount of fertilizer that is considered required is not increased because, in the method and system of the present invention, essentially little or no fertilizer becomes unavailable to the plant.

Long-Felt Need

The present invention is believed to fulfill a long-standing and long-felt need of the agricultural industry and is expected to garner great commercial success attributable to such fulfillment. Further, as seen from the above, the raw materials of the potassium-nutrient feedstock includes a strong mineral acid, namely sulfuric acid, nitric acid, phosphoric acid or combinations these acids, and this mineral acid preferably will be used in the present invention in concentrated form. Also among the raw materials is a strong base, namely potassium hydroxide, and this preferably will be used in the present invention in concentrated form. These potassium-nutrient raw materials possess far too large of a heat of dissolution and heat of reaction (when intermixed) for use in conventional fertigation.

The System of FIG. 1 to FIG. 3

Referring to FIG. 1 and, to the extent components are shown in FIG. 2 and FIG. 3, to FIG. 2 and FIG. 3 also, there is shown a system of the present invention designated by the general reference numeral 10. An agricultural irrigation system distributes irrigation water typically from a water source whether it be a well, surface water (such as water in a canal, reservoir, stream or the like), reclaimed or recycled water. A stream of irrigation water is pumped into a main line (irrigation system main line) and then is filtered. The system 10, as shown in FIG. 1, FIG. 2 and FIG. 3, is an embodiment of an extended system of the present invention because system 10 includes such filters and a segment of such a main line from a point upstream of the filters to a point downstream of the filters, and the addition of potassium-nutrient feedstock raw materials occurs between these two points.

As described below, a segment of a stream of irrigation water that is running between the irrigation-water source and the irrigation line(s) in the field(s) is within the system 10 wherein the irrigation water is first filtered and then treated with the feedstock of the present invention. The system 10 includes a control unit 12, optionally a plurality of filters, which here are shown as sand-media filters 16, an irrigation-water line, which here is shown as a pre-filter (and somewhat higher pressure) segment of an irrigation-water main line, or pre-filter main line 18, which feeds irrigation water (identified and discussed below) through each of the sand-media filters 16, and also through a mixing chamber 14, to a post-filter (and somewhat lower pressure) segment of the irrigation-water main line, or post-filter main line 20. (The post-filter main line 20 is a transport pipe that carries irrigation water to one or more agricultural fields, such as the agricultural field 510 shown in phantom, and obviously not to scale, in FIG. 1. One or more secondary transport pipes service a typical agricultural field, such as transport pipes 520 shown in FIG. 1. Devices for delivering the irrigation water at points in the field, shown as devices 530 in FIG. 1, can be overhead sprinklers or micro-devices (such as emitters or micro-sprinklers.) The feedstock raw materials are stored in separate storage containers 22 which may be conveniently disposed nearby the control unit 12 as shown. As shown, such storage containers or tanks 22 include one for each of the basic raw materials, such as concentrated potassium hydroxide and sulfuric acid. Three additional storage tanks 22 for other materials, such as alternative mineral acid raw materials, such as nitric acid and phosphoric acid, or other materials to be added, including but not limited to extraneous fertilizers, are shown. (The storage tanks 22 are shown staggered for simplicity in showing each of the raw material feed lines 40.)

In other words, the system and method of the present invention requires at least two storage facilities, namely one for the potassium hydroxide and one for the mineral acid, because these raw materials are always charged separately to the water stream. The system and method of the present invention does not exclude the feeding of other (which for practical reasons are preferably compatible) materials and the components required to separately feed such materials.

There is a raw-material feed line 40 between each of the raw-material tanks 22 and the mixing chamber 14. These raw-material feed lines 40 run through the interior of the control unit 12 (not shown in FIG. 1) to the mixing chamber 14. (Only one of such raw-material feed lines 40 is shown running to the mixing chamber 14 for simplicity). For each of the raw materials, and raw-material feed lines 40, there is an injection valve 96 along the raw-material feed line 40 just ahead of the point at which the feed line 40 enters the mixing chamber 14, none of which is shown in FIG. 1 for simplicity, and all of which are shown in FIG. 2 and FIG. 3.

Irrigation water flows to and through each of the sand-media filters 16 through filter feed lines 72. A stream of the irrigation water also flows from the pre-filter main line 18 to the mixing chamber 14 through a mixing-chamber feed line 70, except when the mixing-chamber feed line 70 is closed off. The water flows from the mixing chamber 14 and from each of the sand-media filters 16 discharge to the post-filter main line 20.

Referring now in particular to FIG. 2 (where the storage tanks 22 are again shown staggered for simplicity in showing each of the raw material feed lines 40), each of the raw-material feed lines 40 is equipped with a feed pump 74. Each of these feed pumps 74 is controlled by a flow controller 76 and a master controller 78. Each of these feed pumps 74 is in electrical communication with a flow controller 76 and the master controller 78 (the electrical connections are not shown) and injects or pumps in its respective raw material to its respective feed line 40 at the rate determined by the flow controller 76 and the master controller 78.

The control unit 12 is divided into two chambers, one of which is a lower chamber 82 which houses the feed pumps 74 and a portion of the raw material feed lines 40 downstream of the respective tanks 22 and upstream of the mixing chamber 14. The second chamber of the control unit 12 is an upper chamber 92 which houses the flow controller 76, the master controller 78 and an optional temperature controller 77.

Along each of the raw material feed lines 40 downstream of the respective feed pumps 74 and upstream of the mixing chamber 14 is, as mentioned above, an injection valve 96, each of which is preferably equipped with a backflow preventer (not shown). Along the mixing-chamber feed line 70 are, in the order of from upstream (closest to the pre-filter main line 18) to downstream (closest to the mixing chamber 14) an optional booster pump 98, a mixing-chamber feed-line flow meter 100, a mixing-chamber feed-line flow sensor 102 and a mixing-chamber feed-line shut-off valve 104. The line opposite the mixing-chamber feed line 70 is a mixing-chamber discharge line 71 that is open to the post-filter main line 20. Along the mixing-chamber discharge line 71, in the order of from upstream (closest to the mixing chamber 14) to downstream (closest to the post-filter main line 20), are an optional mixing-chamber discharge-line thermocouple 106 and a mixing-chamber discharge-line shut-off valve 108.

The pre-filter main line 18 is open to the mixing chamber 14 through the mixing-chamber feed line 70, and is open to each of the sand-media filters 16 through filter feed lines 72 or openings. Untreated irrigation water, that is, irrigation water that is not yet treated by the system of the present invention, which is shown by flow arrows and is designated as untreated irrigation water 110 in FIG. 3, flows through the pre-filter main line 18 and discharges to the mixing chamber 14 and the sand-media filters 16 through these respective lines.

As noted above, the mixing-chamber discharge line 71 is open to, and discharges to, the post-filter main line 20, which is best seen in FIG. 3. In addition, each of the sand-media filters 16 is open to, and discharges to, the post-filter main line 20 via filter discharge lines 114 or openings. The untreated irrigation water 110 of the pre-filter main line 18 thus flows to the post-filter main line 20 and therein receives the discharge from the mixing-chamber discharge line 71, becoming irrigation water that carries or has been treated with the potassium-nutrient feedstock of the present invention. Such treated irrigation water is shown by flow arrows and is designated as treated irrigation water 111 in FIG. 3 and elsewhere herein.

Along the post-filter main line 20, in the order of from upstream (closest to the mixing-chamber discharge line 71) to downstream (farthest from the mixing-chamber discharge line 71), are a post-filter main-line pressure gauge 126 and a post-filter main-line flow sensor 128.

Along the pre-filter main line 18, in the order of from upstream (closest to the mixing-chamber feed line 70) to downstream (farthest from the mixing-chamber feed line 70), are a pre-filter main-line pressure sensor 130 and a pre-filter main-line pressure gauge 132.

The storage tanks 22 can vary in size depending on the size and nutrient needs of the irrigation site they serve. Typical storage container sizes are between 300 and 6,500 gallons. The electrical connections between the feed pumps 74 along the raw-material feed lines 40 and the controlling flow controller 76 and master controller 78 each consist separately of an on/off power control (not shown) and a feedback loop (not shown) which controls the output of the respective feed pumps 74, and the construction and operation of such electrical connections are well within the skill of an ordinary person skilled in the art. The upper chamber 92 of the control unit 12, which houses the electrical controls, namely the flow controller 76, the temperature controller 77 and the master controller 78, is isolated from the lower chamber 82 (which houses the feed pumps 74) to avoid, or at least inhibit, corrosion of the electrical components of the electrical controls. The control unit 12 generally is preferably constructed of heavy gauge steel that is anodized to inhibit corrosion. It preferably is secured with a high security lock system (not shown) and is preferably anchored to the ground with several six foot deep spikes (not shown) to prevent tampering and/or theft of the equipment held within the control unit 12.

The flow controller 76 within the control unit 12, which is one of the controls over the feed pumps 74, is also in electrical connection (not shown) with the post-filter main-line flow sensor 128 along the post-filter main line 20. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) The flow controller 76 proportionately varies the input of the raw materials through the respective feed pumps 74 based on the flow rate of the treated irrigation water 111 which is read by the post-filter main-line flow sensor 128 downstream of (beyond) the sand-media filters 16.

The temperature controller 77 within the control unit 12 is in electrical connection (not shown) with the mixing-chamber discharge-line thermocouple 106 along the mixing-chamber discharge-line 71. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) The raw materials from the storage tanks 22 are routed through the respective raw material feed lines 40 and charged to the mixing chamber 14 as the potassium-nutrient feedstock of the present invention. The components of the potassium-nutrient feedstock are intermixed with each other and a stream of untreated irrigation water 110 being fed into the mixing chamber 14 through the mixing-chamber feed line 70. Upon such intermixing, there is an exotherm. The exotherm is the reason the temperature of the potassium-nutrient feedstock and irrigation water mixture is preferably monitored by the mixing-chamber discharge-line thermocouple 106 as the potassium-nutrient feedstock exits the mixing chamber 14. If that temperature is undesirably high, for instance 40° C. or higher (higher than 39° C.), the temperature controller 77 sends a feedback signal to the master controller 78 and the master controller 78 shuts off the feed pumps 74 until a safe temperature is seen at the mixing-chamber discharge-line thermocouple 106, and this off/on sequence is repeated until a safe temperature, as seen at the mixing-chamber discharge-line thermocouple 106, is maintained.

The master controller 78 automatically turns the system 10 on. The master controller 78 is electrically connected (not shown) both to the pre-filter main-line pressure sensor 130 and to the mixing-chamber feed-line flow sensor 102. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) When a minimum pressure (typically 15 psi) is seen at the pre-filter main-line pressure sensor 130 and a minimum flow of water (typically twenty gallons per minute) is seen at the mixing-chamber feed-line flow sensor 102, the master controller 78 actuates the feed pumps 74 and injection valves 96 and any other component of the system 10 which facilitate the treatment of the untreated irrigation water that are then in an inactive state. Upon such actuation, raw materials start feeding to, and mixing in, the mixing chamber 14 (The master controller 78, pre-filter main-line pressure sensor 130 and mixing-chamber feed-line flow sensor 102 are typically always in an active state.). The master controller 78 will not allow such actuation unless both minimums are met. Once the feed pumps 74 and injection valves 96 are actuated, the master controller 78, for safety reasons and preferably, will automatically shut down the feed pumps 74 and injection valves 96 when either of the values seen at the pre-filter main-line pressure sensor 130 and the mixing-chamber feed-line flow sensor 102 falls below its respective minimum, and automatically restart the feed pumps 74 and injection valves 96 when both of the values seen at the pre-filter main-line pressure sensor 130 and the mixing-chamber feed-line flow sensor 102 meet or exceed its respective minimum. In other words, once the flow of untreated irrigation water 110 to the fields begins, it starts flowing (a) through the pre-filter main line 18, (b) to and through the sand-media filters 16, (c) discharging to, and flowing through the post-filter main line 20, and (d) from there to the irrigation lines in the field(s) (not shown), the master controller 78 will actuate the feed pumps 74 and injection valves 96 if the irrigation water is at the normal or expected pressure, flow and flow rate. Note that generally the flow of irrigation will occur as described above regardless of whether the master controller 78 has actuated the feed pumps 74 and injection valves 96 or has shut down the feed pumps 74 and injection valves 96 after initial actuation because that flow sequence and infrastructure are the conventional elements of the irrigation system.

Based on the nutrient-application profile (the type and amount of nutrients that are required for a given time period of the given crop cycle), the master controller 78 automatically determines and sets the correct synchronizations of the feed pumps 74 to provide the desired feedstock raw materials.

As mentioned elsewhere herein, the master controller 78 controls the temperature within the mixing chamber 14, preventing the temperature from straying out of (normally exceeding) the desired range, by shutting off the feed pumps 74 until that temperature drops to, and can be maintained within, the desired range.

When filter(s) are disposed within the path of the irrigation water flowing through the system of the present invention (which is standard but not universal for commercial irrigation systems), such as the sand-media filters 16 shown within the path of the irrigation water between the pre-filter main line 18 and post-filter main line 20 (except the small stream of irrigation water that is routed through the mixing chamber 14), there is normally a small but significant water-flow pressure drop across the filters, such as sand-media filters 16. A flow rate of at least 20 gallons per minute or more of untreated irrigation water 110 through the mixing chamber 14 is preferred, and the optional booster pump 98 is preferably included to provide such flow rate if the pressure drop across the sand-media filters 16 would result in a lower flow rate through the mixing chamber 14 or if a higher flow rate is required to maintain a mixing chamber temperature below 40 degrees C.

As noted elsewhere, disposed along the mixing-chamber feed line 70 are the booster pump 98, the mixing-chamber feed-line flow meter 100, the mixing-chamber feed-line flow sensor 102 and the mixing-chamber feed-line shut-off valve 104. The mixing-chamber feed-line flow meter 100 determines the actual flow rate of untreated irrigation water 110 to, and therefore through, the mixing chamber 14. The mixing-chamber feed-line flow sensor 102 determines if a flow of untreated irrigation water 110 is occurring to, and therefore through, the mixing chamber 14. The flow of raw materials to the mixing chamber 14 will not be permitted unless a flow of untreated irrigation water 110 is occurring through the mixing chamber 14. There of course are electrical connections (not shown) between the mixing-chamber feed-line flow meter 100 and the master controller 78, and between the mixing-chamber feed-line flow sensor 102 and the master controller 78.

The mixing-chamber feed-line shut-off valve 104 is not generally an active element in the operation of the present system, but instead it is an optional, and typically manual, expedient. The mixing-chamber feed-line shut-off valve 104 and the mixing-chamber discharge-line shut-off valve 108 (which likewise is an optional, and typically manual, expedient) can be conveniently used together to isolate the mixing chamber 14 from the flows of irrigation water for maintenance or repair purposes, if ever needed. When the mixing-chamber feed-line shut-off valve 104 and the mixing-chamber discharge-line shut-off valve 108 are open (or in embodiments when they are not present), the small stream of untreated irrigation water 110 flows through the mixing chamber 14 whenever the irrigation water is flowing to the fields (not shown), regardless of whether or not any raw materials are being fed to the mixing chamber 14.

Along the mixing-chamber discharge line 71, downstream of the mixing chamber 14, are the mixing-chamber discharge-line thermocouple 106 which senses the temperature of the potassium-nutrient feedstock and irrigation water mixture as it exits the mixing chamber 14, and sends that data signal (temperature reading) to the master controller 78 for its processing and control of the temperature within the mixing chamber 14 as discussed elsewhere herein. There of course are electrical connections (not shown) between the mixing-chamber discharge-line thermocouple 106 and the master controller 78.

The dispositions and functions of the post-filter main-line pressure gauge 126, pre-filter main-line pressure gauge 130 and the post-filter main-line flow sensor 128 are discussed elsewhere.

The sand-media filters 16 are typically large, for instance 300 gallon, stainless steel filters. Such type of filters is routinely used by growers to remove debris from untreated irrigation water before it enters the irrigation system in the fields. The sand-media filters 16 of the system 10 of the present invention generally and preferably would be filters that are already in place at the given irrigation-system site. As the untreated irrigation water 110 passes through the sand of the sand-media filters 16, the flow of the untreated irrigation water 110 is restricted and that flow restriction causes a small but significant pressure drop across the sand-media filters 16. Such pressure drop is typically in the range of from 5 to 15 psi (but can be higher as debris builds up in the filter), and is the reason that there is a pressure differential between the pre-filter main line 18 and the post-filter main line 20. This pressure drop facilitates a large (fast) flow of untreated irrigation water 110 through the mixing chamber 14 that is needed to temper or mitigate the temperature increase stemming from the exotherms within the mixing chamber 14. (As mentioned elsewhere, if the temperature of the water flowing out the mixing chamber 14 is too high, the charging of potassium-nutrient feedstock to the mixing chamber 14 is halted.) The previously-described optional booster pump 98 is available to create and/or maintain the requisite water flow through the mixing chamber 14, and it is a highly recommended option for irrigation systems that do not have a large enough pressure drop across the filters 16 to provide the requisite cooling by the untreated irrigation water 110 when the potassium-nutrient feedstock is charged to the mixing chamber 14.

In other words, the flow of untreated irrigation water 110 water through the mixing chamber 14 is large (fast) compared to the feed rate (injection rate) of the raw materials into the mixing chamber 14, and thereby quenches any exotherm(s) caused by the charging of potassium-nutrient feedstock to the mixing chamber 14.

The level of potassium-nutrient feedstock that can be charged to the mixing chamber 14 depends on the size of the mixing chamber 14. For any given level, the mixing chamber 14 and the stream of water flowing through it must be sufficiently large to dampen and mitigate the exotherms generated.

In contrast, the system shown in FIG. 4 and described below charges the potassium-nutrient feedstock directly into the irrigation main line, and therefore it intrinsically has a sufficient water flow to dampen and mitigate exotherms generated regardless of the level of potassium-nutrient feedstock charged.

Master controller 78 includes various electronic components that are designed to monitor various electrical signals from the sensing devices. Depending on what signals are input, the master controller 78 turns on the various components of the system once the irrigation system is fully operational and in a mode to insure the proper feed of all the raw materials in the correct proportions, under controlled conditions, to safely produce the potassium-nutrient feedstock inside the irrigation system. Numerous configurations of electric components could be designed to achieve this control. As shown, the master controller 78 consists of various relays, timing devices and power supplies that take the various signals from the sensing equipment and turn on and off the various control systems to safely control the chemical feed pumps 74. (A master controller could of course send the sensing and control data, via wireless communication networks, to an operator stationed in a distant office.) If any incorrect or out-of-range signal is received by the master controller 78 the circuitry inside the master controller 78 responds and sends the appropriate feedback signal to the appropriate device or system to immediately correct the out-of-range condition, change the flow rate of the raw material feed pumps 74 or totally shut off the raw material feed pumps 74.

The system 10 preferably determines and adjusts the pH of the treated irrigation water 111, particularly as illustrated in FIG. 2 and FIG. 3 in which the lower chamber 82 as shown also houses a pH monitoring system 83 which, as shown, is comprised of a pH monitoring-system pump 84, a pH sensor 86, a pH feed line 88 and a pH return line 90, and in which the upper chamber 92 includes a pH controller 80. Also along the post-filter main line 20, in the order of from upstream (closest to the mixing-chamber discharge line 71) to downstream (farthest from the mixing-chamber discharge line 71), are the terminal end 116 of the pH return line 90, the starting end 120 of the pH feed line 88 (along which is a pH line shut-off valve 122 and a solenoid 124). The pH control additives, for instance an acid such as sulfuric acid or phosphoric acid (possibly also potassium hydroxide to raise pH) are preferably stored as concentrated solutions in a storage container(s) served by a feed pump(s) and a feed line(s) as discussed above and illustrated for the raw materials.

When this optional feature is present, the pH controller 80, which is in electrical connection (not shown) with the flow controller 76, might override the flow controller 76 at times for the specific control of the feed pump(s) (such as one of the feed pumps 74 shown) along the feed line (such as one of the feed lines 40 shown) of the sulfuric acid raw material (or other mineral acid raw material or even one or more separate pH-control additives) tank (such as one of the tanks 22 shown) to give the target pH. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.)

The pH controller 80 is electrically connected (not shown) to the pH monitoring system 83. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) The pH controller 80 in conjunction with the pH monitoring system 83 controls the pH of the treated irrigation water 111 as it leaves the system 10. The pH of the treated irrigation water 111 is monitored by diverting a very small stream of treated irrigation water 111 through the starting end 120 of the pH feed line 88 (see FIG. 3) to the pH sensor 86 (see FIG. 2) whereat the pH of that small stream is determined. Based on the pH of the treated irrigation water 111 and based on the feed being produced in the mixing chamber 14, the pH controller 80 adjusts (increases or decreases) the feed of one or more pH adjustment additives to achieve a target treated irrigation water pH. (Under the present invention, a base is optionally available for increasing the pH if needed to achieve a constant target pH, although in practice a pH increase would normally not be required. Further discussion herein of pH adjustment presumes that decreasing the pH is the only adjustment required.) The target treated irrigation water pH is typically a pH of about 6.5, or between 6.5 and 7, and usually is lower than the pH of the untreated irrigation water, because untreated irrigation water is usually alkaline.

The solenoid 124 allows the small stream of the treated irrigation water 111 to be diverted to the pH monitoring system 83 via the pH feed line 88. The master controller 78 will normally and preferably activate the solenoid 124 when it actuates the feed pumps 74 and injection valves 96. The electrical connections between the solenoid 124 and the master controller 78 are not shown.

As mentioned above, a small stream of treated irrigation water 111 is diverted from the post-filter main line 20 to the pH monitoring system 83 through the pH feed line 88 and is returned to the post-filter main line 20 (preferably, as shown, upstream of its diversion point) through the pH return line 90. Along the starting end 120 of the pH feed line 88 is a pH feed-line shut-off valve 122. Along the terminal end 120 of the pH return line 90 is a pH return-line shut-off valve 123. The pH feed-line shut-off valve 122 and the pH return-line shut-off valve 123 are not normally active elements of the system 10 but instead are optional, and typically manual, expedients which can be conveniently used together to isolate the pH monitoring system 83 from the flows of irrigation water for maintenance or repair purposes, if ever needed, without discontinuing the irrigation water flow through the remainder of the system 10.

The small stream of treated irrigation water 111 that is diverted from the post-filter main line 20 at the starting end 120 of the pH feed line 88 feeds into the pH monitoring system 83 through the pH feed line 88. (The starting end 120 of the pH feed line 88 as seen in FIG. 3 and the pH feed line 88 as seen in FIG. 2 are opposite ends of a single flow line.) The pH of that small stream is read by the pH sensor 86 of the pH monitoring system 83. Electrical connections between the pH sensor 86 and the pH monitoring system 83 exist but are not shown. The pH monitoring-system pump 84 pumps the small stream through the pH monitoring system 83, and the pH monitoring-system pump 84 is controlled by the master controller 78 (electrical connections between these elements are not shown.)

To summarize, the pH monitoring system 83 includes the pH monitoring-system pump 84 which pumps treated irrigation water 111 from the post-filter main line 20 through the pH feed line 88, past the pH sensor 86, and then back to the post-filter main line 20 through the pH return line 90. The electrical connections between the pH monitoring system 83 and the pH controller 80 are not shown.

The solenoid 124 shuts off treated irrigation water 111 flow from the post-filter main line 20 through the starting end 120 of the pH feed line 88 when the water-flow pressure seen at the pre-filter main-line pressure sensor 130 and/or at the mixing-chamber feed-line flow sensor 102 drop below predetermined threshold values. The solenoid 124 is in electrical connection (not shown) with the master controller 78.

The System of FIG. 4

Referring to FIG. 4, there is shown a segment of a system of the present invention designated by the general reference numeral 310, which differs from the system 10 of FIG. 1 to FIG. 3 by the omission of a separate mixing chamber component such as the mixing chamber 14 of the embodiment shown in FIG. 1 to FIG. 3. In the system 310 of FIG. 4, the raw material feed lines 340 (only two shown for simplicity) feed directly into a main line (as shown, into the main line segment that is the post-filter main line 320.

The system 310 includes a control unit 312 (partially shown in FIG. 4), a plurality of filters 316, an irrigation-water line or main line (which is designated in two segments, namely a pre-filter main line 318 and a post-filter main line 320) and filters 316 along the main line between its pre-filter segment (pre-filter main line 318) and its post-filter segment (post-filter main line 320). Components of system 310 that are not shown in FIG. 4 include the components within the control unit 312, namely a lower chamber which houses a feed-line feed pump, pH monitoring-system pump, a pH sensor, a pH feed line and a pH return line, and also an upper chamber which houses a flow controller, a master controller, a pH controller and a temperature controller. Other components of system 310 that are not shown in FIG. 4 include at least two storage containers (one for each of two raw materials, although this system 310 could just as well have more storage containers to hold other materials as discussed above for system 10 of FIG. 1 through FIG. 3). In each instance the components of system 310 that are not shown in FIG. 4, and their electrical connections, are analogous to those described above for the system 10 shown in FIG. 1 to FIG. 3, and therefore no further description is needed here. Further, the components of system 310 that are shown in FIG. 4, and their electrical connections, also are analogous to those described above for the system 10 shown in FIG. 1 to FIG. 3, except as explicitly stated otherwise herein, and therefore little or no further description is needed here.

As mentioned above, there is a raw-material feed line 340 between each of the two raw-material tanks (not shown) and the post-filter main line 320. These raw-material feed lines 340 run through the interior of the control unit 312 and, as seen in FIG. 4, from there to the post-filter main line 320. For each of the raw materials, and raw-material feed lines 340, which for system 310 is two raw materials and two raw-material feed lines 340, there is an injection valve 396 along the raw-material feed line 340 just ahead of the point at which the feed line 340 enters, or discharges to, the post-filter main line 320.

Irrigation water flows to and through each of the filters 316 through filter feed lines 372, and discharges from each of the filters 316 to the post-filter main line 320. The raw materials also discharge to the post-filter main line 320 (via the feed lines 340) and along each of the raw material feed lines 340 upstream of the post-filter main line 320 is, as mentioned above, an injection valve 396, each of which is equipped with a backflow preventer (not shown).

In system 310, unlike the system 10 shown in FIG. 1 to FIG. 3, not only is there no separate mixing chamber component, there is no mixing-chamber feed line, no optional booster pump, no mixing-chamber feed-line flow meter, no mixing-chamber feed-line flow sensor, no mixing-chamber feed-line shut-off valve, no mixing-chamber discharge line and no mixing chamber discharge-line shut-off valve. There is a component that is the functional equivalent of the mixing-chamber discharge-line thermocouple 106, and that is a post-filter main-line thermocouple 406 that is positioned along the post-filter main line 320 downstream of the points at which the feed lines 340 discharge to the post-filter main line 320. The post-filter main-line thermocouple 406 (“thermocouple 406”), like the mixing-chamber discharge-line thermocouple 106 of system 10, tracks the exotherms by monitoring the irrigation-water temperature in the water stream to which the feedstock is charged.

The pre-filter segment of the main line (pre-filter main line 318) is open to each of the filters 316 through filter feed lines 372 or openings. Untreated irrigation water, that is, irrigation water that is not yet treated by the system of the present invention, which is shown by flow arrows and is designated as untreated irrigation water 410 in FIG. 4, flows through the pre-filter main line 318 and discharges to the filters 316 through the respective filter feed lines 372. In addition, each of the filters 316 is open to, and discharges to, the post-filter main line 320 via filter discharge lines 314 or openings. The untreated irrigation water 410 thus flows through the filters 316 and thereafter receives the charge of raw materials from their feed lines 340, becoming treated irrigation water that carries or has been treated with the feedstock of the present invention. Although charging the feedstock along a post-filter section of the main line (post-filter main line 320) is preferred, charging the feedstock along a pre-filter section of the main line (pre-filter main line 318) is not excluded from the present invention. The feedstock charge should, however, be pre-delivery (upstream of the point(s) of delivering the irrigation water to the crop). Such irrigation water is shown by flow arrows and is designated as treated irrigation water 411 in FIG. 4 and elsewhere herein.

Along the post-filter main line 320, in the order of from upstream (where the stream of irrigation water has not flowed past the feed lines 340 and therefore the water is filtered but not yet irrigation water 409) to downstream (farthest along the post-filter main line 320), are a post-filter main-line pressure gauge 426 and a post-filter main-line flow sensor 428.

Along the pre-filter main line 318, in the order of from upstream (closest to the water source, not shown) to downstream, are a pre-filter main-line pressure sensor 430 and a pre-filter main-line pressure gauge 432.

The temperature controller (not shown) within the control unit 312 is in electrical connection (not shown) with the thermocouple 406 along the post-filter main line 320. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) The raw materials from the various storage tanks (not shown) are routed through the respective raw material feed lines 340 and charged to the post-filter main line 320 as the potassium-nutrient feedstock of the present invention. The components of the potassium-nutrient feedstock intermix with each other and the relatively large stream of filtered irrigation water 409 flowing out from the filters 316. Upon such intermixing, there is an exotherm from the heat of dissolution and reaction of the raw materials. This exotherm is the reason the temperature of the potassium-nutrient feedstock and irrigation water mixture is preferably monitored by the thermocouple 406 downstream of the points at which the feed lines 340 discharge the raw materials to the post-filter main line 320. If that temperature is undesirably high, for instance 40° C. or higher (higher than 39° C.), the temperature controller (not shown) sends a feedback signal to the master controller (not shown) and the master controller shuts off the feed pumps (not shown) until a safe temperature is seen at the thermocouple 406, and this off/on sequence is repeated until a safe temperature, as seen at the thermocouple 406, is maintained. The volume and flow of irrigation water 409 in the post-filter main line 320 are, however, far greater than that through the mixing chamber 14 of system 10 shown in FIG. 1 to FIG. 3, and therefore the likelihood of an excessively high temperature being seen at the thermocouple 406 approaches negligible, regardless of the concentration of raw materials which are being fed, outside of, of course, a major water-flow problem in the irrigation system itself.

The master controller (not shown) automatically turns the system 310 on. The master controller is electrically connected (not shown) to the pre-filter main-line pressure sensor 430. (The construction and operation of these electrical connections are well within the skill of an ordinary person skilled in the art.) When a minimum pressure (typically 15 psi) is seen at the pre-filter main-line pressure sensor 430, the master controller actuates the feed pumps (not shown) and injection valves 396 and any other component of the system 310 which facilitate the treatment of the irrigation water that are then in an inactive state. Upon such actuation, raw materials start feeding to the post-filter main line 320 as the potassium-nutrient feedstock of the present invention. The master controller will not allow such actuation unless the minimum is met. Once the feed pumps (not shown) and injection valves 396 are actuated, the master controller, for safety reasons and preferably, will automatically shut down the feed pumps and injection valves 396 when the value seen at the pre-filter main-line pressure sensor 430 falls below its minimum, and automatically restart the feed pumps and injection valves 396 when the value seen at the pre-filter main-line pressure sensor 430 meets or exceeds its respective minimum. In other words, once the flow of untreated irrigation water 410 to the fields begins, the irrigation water starts flowing (a) through the pre-filter main line 318, (b) to and through the filters 316, (c) discharging to, and flowing through the post-filter main line 320, and (d) from there to the irrigation lines in the field(s) (not shown), and when this flow starts, the master controller will actuate the feed pumps and injection valves 396 provided this irrigation water flow is at the normal, or expected, pressure, flow and flow rate. Note that generally the flow of irrigation will occur as described above regardless of whether the master controller has actuated the feed pumps and injection valves 396 or has shut down the feed pumps and injection valves 396 after initial actuation because that water flow sequence and infrastructure are the conventional elements of the irrigation system.

The starting end 420 of the pH feed line is downstream of the point(s) at which the raw materials are charged to the post-filter main line 320 and therefore, as in system 10 shown in FIG. 1 to FIG. 3, it is the pH of the treated irrigation water 411, not the irrigation water prior to treatment, which is being monitored by diverting a very small stream of treated irrigation water 411 through the starting end 420 of the pH feed line to the pH sensor (not shown) whereby the pH controller (not shown) adjusts (increases or decreases) the feed of acid(s) and/or base(s) to achieve a constant target treated irrigation water pH. The target treated irrigation water pH is typically a pH of about 6.5. Along the post-filter main line 320, in the order of from upstream (where the stream of irrigation water has not flowed past the feed lines 340 and therefore the water is filtered but not yet irrigation water 409) to downstream (farthest along the post-filter main line 320), are the terminal end 416 of the pH return line, the raw material feed lines 340 and the thermocouple 406 (both mentioned above), the starting end 420 of the pH feed line (along which is a pH line shut-off valve 422 and a solenoid 424), a post-filter main-line pressure gauge 426 and a post-filter main-line flow sensor 428 (both mentioned above).

Again, the remainder of the system 310 is analogous to the system 10 shown in FIG. 1 to FIG. 3 and described in detail above. Further, as described above for system 310, the “mixing chamber” concept is part of, or within, the irrigation main line, namely the post-filter section of the irrigation main line (post-filter main line 320). The dilution of the potassium-nutrient feedstock in this far greater water stream is of course highly increased, thereby minimizing the exotherms even more than is possible with a separate mixing chamber component such as the mixing chamber 14 of system 10. Further, system 310 is simpler than system 10 because most of the controls associated with a separate mixing chamber component such as the mixing chamber 14 of system 10 are eliminated, as described above, and even the thermocouple 406 may be an unnecessary safety component because the level of potassium-nutrient feedstock being charged is so extremely low in comparison to the volume of irrigation water to which it is being charged.

Example 1 and Comparative Example A Projections

The method of the present invention in comparison to conventional fertilization practices was evaluated for use at a 150 acre almond ranch that has been using conventional fertilization practices for years. For this comparison, a fertigation program similar to that used in the past was selected for the projection of Comparative Example A, namely, the addition of 175 lb/acre potassium (as K2O) for a single crop cycle. The projection of Example 1 is 125 lb/acre potassium (as K2O) which is approximately 25 percent lower because, as discussed above, a far higher percentage of the nutrients applied are available to the crop in comparison to conventional fertilization practices such as those of Comparative Example A. The downward adjustment of the nutrient profile for the method of the present invention is a very conservative estimate of the lower nutrient levels required when nutrients are no longer being lost to the root area as described above for conventional fertilization.

The agricultural area of this Example 1 and Comparative Example A, namely the 150 acre almond ranch, will normally receive a total of four acre-feet of irrigation water over its eight-month (March 1 to November 1) growing season, delivered as follows: (a) 1.0 acre-foot during the first three months (March 1 through June 1); 2.5 acre-feet during the second three months (June 1 through September 1); and 0.5 acre-foot during the last two months (September 1 through November 1). An acre-foot is 325,851 gallons, and therefore 195.5 million gallons of irrigation water are delivered to the acreage of this ranch per growing season.

In Comparative Example A, the source of potassium used is potassium thiosulfate (K2S2O3) added as a 25 wt. percent aqueous solution (a conventional 0-0-25 NPK fertilizer). This fertilizer is slug fed to the irrigation system in the amounts of 400 lb/acre on March 15 and 300 lb/acre on September 15 to provide a fertigation of 100 lb/acre potassium (as K2O) on March 15 and 75 lb/acre potassium (as K2O) on September 30.

In Example 1, the source of potassium used is potassium hydroxide added as concentrated potassium hydroxide, a 50 wt. percent solution (a 0-0-42 NPK potassium source), which is continuously added with the irrigation water together with sufficient sulfuric acid to react with (neutralize) the potassium hydroxide and lower the pH of the treated irrigation water to 6.5. The amount of potassium (as K2O) fed is 50 lb/acre during the March, April and May three-month time interval period, 25 lb/acre during the June, July and August three-month time period, and 50 lb/acre during the September, October and November three-month time period.

Comparative Example A and Example 1 Projection Comparisons:

Slug Feed—Comparative Example A Projection (Potassium (as K2O)):

On March 15 potassium (as K2O) is slug fed into the irrigation system. Specifically, 100.0 lbs./acre potassium (as K2O) from a potassium thiosulfate source is fed to 150 acres at a flow rate of 1200 gallons/min. for this grower's normal 9.0 hour irrigation period. The potassium (as K2O) concentration in the irrigation water during this slug fertigation process is: (100.0 lbs./acre potassium (as K2O)×150 acres×1000 grams/2.2 lbs.)/(1200 gal./min.×9 hrs.×60 min./hr.×3.78 liters/gal.×1000 ml/1 liter) or 2784 ppm potassium (as K2O). This high concentration of potassium (as K2O) cannot be fed simultaneously with the slug feeding of other fertilizers because of incompatibilities with other fertilizers and the lack of available equipment.

The amount of water used during this slug fertigation process is, using the parameter that an ac-ft (acre-foot) is 325,851 gallons of water: 1200 gal./min.×60 min./hr.×9 hrs. or 648,000 gal.×1 ac-ft/325,851 gal. or 1.99 ac-ft. The 1.99 ac-ft of water is distributed over 150 acres and therefore the per-acre water distribution (1.99 ac-ft/150 acres) is 0.0133 ac-ft/acre.

The next slug feed fertigation of potassium is September 30. The total evenly-distributed irrigation water to be delivered during the second half of March, April and May is 1 ac-ft. Therefore the amount of irrigation water delivered during the period of March 16th (the day after the March 15th slug feeding) and May 31st is about “1 ac-ft/acre×(2.5 months/3.0 months)” or 0.833 ac-ft/acre, and it will contain no potassium (as K2O) fertilizer. The total evenly distributed irrigation water to be delivered during the period from June 1 through August 31 is 2.5 ac-ft/acre and again will contain no potassium (as K2O). The total evenly distributed irrigation water to be delivered during the period from September 1 through September 29 (the day before the September 30th slug feeding) is about “0.5 ac-ft/acre×1.0 month/2 months)” or 0.25 ac-ft and it will again contain no potassium (as K2O). As a result of this slug feed addition profile, there are about [(3.583 ac-ft/acre)/0.0133 ac-ft)−1]” or 268.4 irrigation periods during which no potassium (as K2O) is delivered with the irrigation water between March 15 through September 29. To adequately irrigate the almond crop, approximately 269 9-hour irrigation periods are required. Since there are only 197 days between March 16 and September 29 there are some days (hotter weather) when there are two 9-hour irrigation periods (or the equivalent) to achieve the required amount of irrigation.

Continuous Feed—Example 1 Projection (Potassium (as K2O)):

A total of 50.0 lbs./acre potassium (as K2O) is continuously charged at a low concentration (18.5 ppm potassium (as K2O) as shown below) to the irrigation water distributed during each irrigation period during the months of March, April and May (from March 1 up to, but not including, June 1). This low concentration of potassium (as K2O), unlike the high concentration slug fed as described above, can be charged simultaneously with other low-concentration fertilizer feedstocks, and therefore this continuous feeding begins on the desired March 1 date.

For purposes of comparison to the slug-fed projection above, only the potassium (as K2O) charged, and the irrigation water delivered, during the time period of between March 15 and May 31 is compared. The comparative (normalized) amount of potassium (as K2O) charged between March 15 and May 31 is 41.7 lbs./acre potassium (as K2O). The potassium (as K2O) concentration in the irrigation water during this continuous fertigation process is: (41.7 lbs./acre×150 acres×1000 grams/2.2 lbs.)/(0.833 ac-ft/acre×325,851 gal./ac-ft×3780×150 acres) or 18.5 ppm potassium (as K2O).

In other words, in this Example 1 projection, potassium is continuously delivered with the 0.833 ac-ft of irrigation water delivered during the 62.6 nine-hour irrigation periods from March 1 through May 31, while in the Comparative Example A projection, the entire fertilizer is added only during the first nine-hour irrigation period. Further, the potassium (as K2O) charged in Example 1 is 25% less than in Comparative Example A because, given the rate of potassium uptake by a plant, this 25% lower amount is sufficient to maintain a constant supply of potassium in the wetted root zone throughout the March 1 through May 31 time period. In contrast, the higher amount of potassium is required in Comparative Example A to at least partially compensate for the amount of potassium in the single slug feeding that is later washed away from the wetted root zone before uptake by a plant.

Again, another difference between the slug feeding of Comparative Example A and the present invention's continuous feeding of Example 1 is the rate of fertilizer addition. Again to fully illustrate the magnitude of this difference, the feed rates are provided below.

Slug Feed—Feed Rate of Comparative Example A Projection (Potassium (as K2O)):

In the slug feeding projection of Comparative Example A, the source of the 100 lbs./acre of potassium (as K2O) is a potassium thiosulfate (K2S2O3) feedstock which is 25.0 percent potassium (as K2O) and has a density of 12.64 lbs./gal. The volume of the potassium thiosulfate feedstock used is: 150 acres×100.0 lbs./acre potassium (as K2O)×100%/25.0%×1 gal./12.64 lbs. or 4747 gallons. This 4747 gallons is then applied to the 150 acres in a 9.0 hr. period which means the feed rate is: 4747 gal./9.0 hrs.×1 hr./60 min.=8.79 gal./min. (continuously throughout a nine hour irrigation period).

Continuous Feed—Feed Rate of Example 1 Projection (Potassium (as K2O)):

In the continuous feeding projection of Example 1, which again will be illustrated as the normalized (March 15 through May 31) feeding of 41.7 lbs. of potassium (as K2O), the source is a potassium hydroxide feedstock having 42% potassium (as K2O) and a density of 12.51 lb./gal. The volume of potassium hydroxide feedstock used is: 150 acres×41.7 lbs./acre potassium (as K2O)×100%/42%×1 gal./12.51 lbs. or 1784 gallons. The feed rate of this 1784 gallons, which is charged continuously for delivery to 150 acres 62.6 nine-hour irrigation periods, is: 1784 gal./62.6 periods×1 period/9.0 hrs.×1 hr./60 min. or 0.0528 gal./min.

Therefore the feed rate of the present invention's Example 1 projection is 0.0558/8.79, or 0.6%, that of the feed rate of the Comparative Example A projection. In other words, the feed rate of the Comparative Example A projection is 8.79/0.0558, or 158% faster than the feed rate of the present invention's Example 1 projection. In other words, the conventional slug-feeding feed rate is 8.79 gal./min. for a potassium addition of 100.0 lbs./acre (as K2O), the continuous-feed feed rate of the present invention is 0.0528 gal./min. for a potassium addition of 50.0 lbs./acre (as K2O), and therefore the slug-feed is (8.79 gal./min)/(0.0528 gal./min.) or 158 times faster.

Continuous Feed—Responsive to Shifting Conditions, Example 1 Projection (Potassium (as K2O)):

Although this Example 1 projection for potassium is for a distinct irrigation period, it is easily seen that if the weather changes or a crops need changes their nutrient profile for any reason, the method and system of the present invention is, or preferably is, responsive to those changes. In contrast, once a single shot (slug feeding) of a potassium fertilizer is delivered to the crop as in the conventional method (such as shown in Comparative Example A), no responsive changes can be made because everything has already added to the soil. The method of the present invention, unlike the conventional slug feeding method, is not locked in to any amount or any feed rate of the potassium source.

Continuous Feed—Absence of Plugging, Example 1 Projection (Potassium (as K2O)):

Adding a KOH feedstock to an irrigation system in any conventional manner would cause severe plugging of the irrigation system and be detrimental to plant grower because it is extremely alkaline (pH>14). In the continuous feeding method of the present invention, the potassium hydroxide is neutralized with an acid. If that acid were simply concentrated H2SO4 (98%), the amount of acid used would be: 50.0 lbs/acre (as K2O)×150 acres×(98.0 g/mole)/(94.2 g/mole)×100%/98% H2SO4×1 gal./15.30 lbs. or 520 gallons, which would be charged at a rate of: 520 gal./62.6 cycles×1 cycle/9.0 hrs.×1 hr./60 min. or 0.0154 gal./min. (over 62.6 fertigation periods).

Comments on In-Situ Fertilizer Manufacture

The method and system of the present invention can use all or any of the concentrated raw materials that are used to manufacture the commercial potassium fertilizers, namely potassium hydroxide, nitric acid, sulfuric acid and phosphoric acid, right at the irrigation site. When these raw materials are charged, the following reactions take place to some extent until an equilibrium is reached:

-   -   1). HNO3+KOH→KNO3+H2O+heat of reaction     -   2). H2SO4+KOH→KHSO4+H2O+heat of reaction     -   3). H2SO4+2KOH→K2SO4+2H2O+heat of reaction     -   4). H3PO4+KOH→KH2PO4+H2O+heat of reaction     -   5). H3PO4+2KOH→K2HPO4+2H2O+heat of reaction     -   6). H3PO4+3KOH→K3PO4+3H2O+heat of reaction     -   7). HNO3+KOH→KNO3+H2O

In solution these transient compounds immediately dissociate into the following ionic species with the formation of additional heat: (a) the cation K+; and (b) the anions NO3-, H2PO4-, HPO4-2, PO4-3, HSO4- and SO4-2.

If the growing conditions (and therefore the desired anion addition or the desired fertilizer addition) change, the raw materials being charged can be changed to best suit conditions at a moments notice.

Example 2 and Comparative Example B Projections

The fertigation projections for a ranch having 453 acres of almonds under cultivation were developed using conventional fertigation techniques in Comparative Example B and, for comparison, the method and system of the present invention in Example 2. The expected irrigation period for the crop is March 1 through October 30. The irrigation system on this ranch does not allow simultaneous irrigation of the entire 453 acres. Instead, the 453 acres are irrigated in five portions or sections, and a set of valves switches the water flow from one section to another. Fertigation of course must likewise be conducted in five portions or sets, that is, one set for each of the five sections. Slug-fed fertigation for a set typically requires feeding the material into the irrigation system for a time period of six to seven hours, and then this is repeated the following day for the next set, until all sections are fertigated in five sets usually over a five-day time period. The continuous-feed fertigation of Example 2 is of course ongoing whenever the irrigation system is active and is at the appropriate water-flow level as described elsewhere.

The potassium nutrient profile and the materials and amounts thereof (lb./acre) to be fed for the conventional slug-fed fertigation with commercial fertilizers of Comparative Example B and the present invention's continuous in-situ manufacturing fertigation of Example 2 are provided below.

Comparative Example B: Conventional Slug-Fed Fertigation with Commercial Fertilizers

Meeting the nutrient profile below requires four fertigations (each designated by the first date of a series of five fertigation sets) and the addition of a single commercial fertilizer at a single feed point along the irrigation system's main line for each fertigation. The number of fertigation sets therefore is twenty. The total poundage fed to the system is significantly higher than that of Example 2.

Potassium (as K2O) Profile:

180 lbs./acre Total Potassium. The potassium will be obtained from variety of commercially available fertilizers: Commercial (0-0-25); Commercial (4-6-10); and Commercial (0-0-5). This is to be added during the following intervals: March 1 through May 31, 100 lbs./acre of total potassium (as K2O); June 1 through August 31, 25 lbs./acre of total potassium (as K2O); September 1 through October 30, 55 lbs./acre of total potassium (as K2O).

pH Profile:

No adjustment (pH is the pH of the incoming irrigation water, which is about 7.8, which might be somewhat modified by the slug-feedings).

Commercial Fertilizers Fed and Nutrients Provided:

March 15 Commercial Fertilizer Fed and Nutrients Provided:

Slug-feed 333.2 lbs./acre of a commercial mixture called K-Mend® (K-Mend® is a registered trademark of Best Sulfur Products, Inc. of Fresno, Calif.) which is derived from potassium thiosulfate (0-0-25). This slug-feed provides 83.3 lbs./acre of potassium (as K2O).

May 1 Commercial Fertilizer Fed and Nutrients Provided:

Slug-feed of 167.2 lbs./acre of a blended commercial mixture called Cache® (Cache® is a registered trademark of Actagro, LLC of Biola, Calif.) which is derived from ammonia, urea, ammonium nitrate, phosphoric acid and potassium chloride (4-6-10). This slug-feed provides: (a) 3.7 lbs./acre of ammoniacal nitrogen (as N); (b) 1.0 lbs./acre of nitrate nitrogen (as N); (c) 2.0 lbs./acre of urea nitrogen (as N); (d) 10.0 lbs./acre of phosphorus (as P2O5); and (e) 16.7 lbs./acre of potassium (as K2O).

June 15 Commercial Fertilizer Fed and Nutrients Provided:

Slug-feed 100.0 lbs./acre of a commercial mixture called K-Mend® (K-Mend® is a registered trademark of Best Sulfur Products, Inc. of Fresno, Calif.) which is derived from potassium thiosulfate (0-0-25). This slug-feed provides 25.0 lbs./acre of potassium (as K2O).

October 30 Commercial Fertilizer Fed and Nutrients Provided:

Slug-feed 1100.0 lbs./acre of a blended commercial mixture called Potassium sulfate solution which is derived from potassium sulfate (0-0-5). This slug feed provides 55.0 lbs./acre of potassium (as K2O).

Example 2 Continuous In-Situ Manufactured Fertigation of the Present Invention

The nutrient profile (below) is satisfied with a continuous feeding of a plurality of potassium-nutrient-feedstock raw materials and any other desired materials, simultaneous charged at separate, but proximate, feed points along the irrigation system's main line. The total poundage fed to the system is significantly lower.

Potassium (as K2O) Profile:

180 lbs./acre Total Potassium. The potassium will be obtained from concentrated potassium hydroxide. This is to be added continuously during the following intervals: March 1 through May 31, 100 lbs./acre of total potassium (as K2O). June 1 through August 31, 25 lbs./acre of total potassium (as K2O). September 1 through October 30, 55 lbs./acre of total potassium (as K2O).

pH Profile:

Continuously adjust to a pH of 6.5 March 1 through October 30: The exact amount of sulfuric acid that is added is dependent on both the alkalinity resulting from the potassium hydroxide raw material, as offset by the addition of any other mineral acid, as well as the alkalinity of any other species being added and the irrigation water. This amount is determined by the pH controller, which always maintains the pH at the desired level. In this case the target pH is set at 6.5.

Charges and Nutrients Provided:

March 1 through May 31 Charges and Nutrients Provided:

Continuous simultaneous charge and reaction of the following co-reactant raw materials: 238.08 lbs./acre potassium hydroxide, concentrated nitric acid and sulfuric acid (as required in combination to neutralize the potassium hydroxide and maintain a target pH of 6.5 for the treated irrigation water). This continuous charge provides 100.00 lbs./acre potassium (as K2O).

June 1 through August 31 Charges and Nutrients Provided:

Continuous simultaneous charge and reaction of the following co-reactant raw materials: 59.52 lbs./acre potassium hydroxide and concentrated nitric acid, phosphoric acid and/or sulfuric acid (as required in combination to neutralize the potassium hydroxide and maintain a target pH of 6.5 for the treated irrigation water). This continuous charge provides 25.00 lbs./acre potassium (as K2O).

September 1 through October 30 Charges and Nutrients Provided:

Continuous simultaneous charge and reaction of the following co-reactant raw materials: 130.96 lbs./acre potassium hydroxide and nitric acid, phosphoric acid and/or sulfuric acid (as required in combination to neutralize the potassium hydroxide and maintain a target pH of 6.5 for the treated irrigation water). This continuous charge provides 55.00 lbs./acre potassium (as K2O).

Summary and Comments on Comparative Example B, October 30 Potassium Addition

On October 30, potassium thiosulfate was not available commercially, and therefore on October 30 no commercial fertilizer derived from potassium thiosulfate was available to the grower. As a result of the unavailability of a commercial potassium thiosulfate fertilizer to meet the potassium requirements of the crop, the grower was forced to have a fertilizer company manufacture a potassium sulfate fertilizer. Due to the low solubility of potassium sulfate, the grower had to ship, store and fertigate with 1100.0 lbs./acre of a dilute potassium sulfate fertilizer solution (0-0-5) which resulted in an extreme expense and inconvenience.

The present invention in some embodiments is a system for continuous fertigation of an agricultural field under the irrigation of an active agricultural irrigation system. Such continuous fertigation includes charging a potassium-nutrient feedstock to the active agricultural irrigation system, wherein the active agricultural irrigation system has flowing irrigation water upstream of the agricultural field. The potassium-nutrient feedstock is comprised of a plurality of feedstock raw materials (which are also referred to herein as potassium-nutrient raw materials and raw materials), and such raw materials generate an exotherm upon intermixing with each other and with the irrigation water.

The system for continuous fertigation has a plurality of potassium-nutrient raw-material feed points open to a stream of flowing irrigation water. The feed points are sufficiently proximate each other and the stream of the irrigation water has sufficient flow to intermix the plurality of potassium-nutrient-feedstock raw materials with each other and with the stream of flowing irrigation water. The feed points are each preferably spaced-apart from the neighboring feed points a distance of no more than about 10 inches, and more preferably no more than about 8 inches because, in preferred embodiments, the pH of the post-feed (treated) irrigation water is monitored upstream of the agricultural field. The length of the mainline along which such pH monitoring occurs might be twenty to thirty feet, or it might be only a few feet. In the former instances, closely proximate feed points and the positioning of the feed points well upstream of the pH monitoring point allows a good intermixing of the potassium-nutrient-feedstock raw materials ahead of the pH monitoring point. In the latter instances, closely proximate feed points positioned as far upstream of the pH monitoring point as practically possible are needed to provide a reasonable degree of intermixing of the potassium-nutrient-feedstock raw materials ahead of the monitoring point.

The stream of irrigation water also has a sufficient flow to dampen the dissolution and reaction exotherms. In an irrigation system, the ambient temperature of the irrigation water depends on a number of factors, including the time of year (which impacts ambient outdoors air temperature) and the ambient temperature of the water source (which varies from very cold water, such as snow run-off, to rather warm water, such as well water in geothermal areas) and it can range from 35 to 100 degrees F. An excessive, and in instances dangerous, increase in water temperature would ensue if the irrigation water were static or had an insufficient flow to dampen the exotherms. A sufficient flow is difficult to adequately describe in terms of flow rates because main-line diameters and other factors differ drastically from one irrigation system to another. Therefore the sufficiency of flow is better described in terms of its ability to dissipate the heat of the exotherms, which in turn is measurable by the increase, if any, in the ambient water temperature of the irrigation water. In the present invention generally, an increase in temperature over ambient water temperature (which again can be very cold to rather warm) is no more than about 60 degrees F. and is dependent on the raw materials being fed, and rate at which they are being fed, and individual characteristics of the irrigation system being served. In preferred embodiments the dissolution and reaction exotherms are dampened to the extent that a temperature increase is no more than 40 degrees F. over ambient irrigation water temperature, and more preferably no more than 20 degrees F. over ambient irrigation water temperature.

When the plurality of potassium-nutrient-feedstock raw materials are being fed, the system of the present invention has means for simultaneously feeding the plurality of potassium-nutrient-feedstock raw materials to the stream of flowing irrigation water whereby treated irrigation water is formed. As described above for the systems shown in FIG. 1 to FIG. 4, such means can include feed lines, each running from a supply of a potassium-nutrient feedstock raw material to a feed point, and the various controls described for activating and maintaining the simultaneous feeding of potassium-nutrient-feedstock raw materials to the stream of flowing irrigation water. Upon the feeding of the potassium-nutrient-feedstock raw materials to the stream of flowing irrigation water, they intermix with each other and intermix with the irrigation water, and convert the irrigation water to treated irrigation water (the irrigation water now being a vehicle carrying the potassium nutrient (s) to the agricultural field).

The irrigation system includes means for irrigating the agricultural field with the treated irrigation water, which means are the transport pipe lines and micro-irrigation type of emitters or the like, or overhead sprinkling systems.

The plurality of potassium-nutrient raw-material feed points preferably open to a high-dilution environment and therefore the potassium-nutrient-feedstock raw materials are fed to a high-dilution environment. Feeding to such a high-dilution environment is preferred because a greater dampening of exotherms will be realized. Embodiments of the system of the present invention in which the potassium-nutrient-feedstock raw materials are fed to a high-dilution environment include feeding to the stream of flowing irrigation water flowing through the main line of an irrigation system at a section upstream of the agricultural field, and in such embodiments the plurality of feed points are disposed along the main line. Embodiments of the system of the present invention in which the potassium-nutrient-feedstock raw materials are fed to a high-dilution environment also include feeding to a stream of irrigation water flowing through a side-arm mixing chamber (which discharges to the main line) and then the plurality of feed points are disposed along the side-arm mixing chamber. In the latter instance, the fast flow and discharge to the main line are a sufficiently high-dilution environment to dampen exotherms although monitoring the water temperature in this region is typically prudent while monitoring water temperature in the former embodiments is typically unnecessary.

In preferred embodiments, the system of the present invention includes means to commence the feed of the potassium-nutrient-feedstock raw materials upon the water stream reaching a first pre-selected degree of flow, means to halt the feed upon the stream reaching a second pre-selected degree of flow, and means to separately provide a pre-selected degree of feed through each of feed points, such as the components described above for the systems shown in FIG. 1 through FIG. 4.

In preferred embodiments, the system of the present invention includes means to determine the pH of the treated irrigation water upstream of the agricultural field, such as the components described above for the systems shown in FIG. 1 through FIG. 4. The point for determining the pH of the treated irrigation water is of course downstream of the feed points because irrigation water is converted to treated irrigation water only upon receiving the raw materials. Preferably the pH of the treated irrigation water has sufficient time to stabilize prior to being monitored and therefore the monitoring of the pH, or the sampling for the pH monitoring, is as far downstream of the feed points as practicalities permit. For this same reason, namely to space apart the feed points and pH monitoring point, the feed points are preferably close to each other, for instance no more than about ten inches apart from adjacent feed points. A distance between adjacent feed points of from about six to about eight inches is very practical. When the length of main line available is short, for instance only about three feet, the feed points are preferably placed as far upstream as possible and the pH monitoring point is placed as far downstream as practical so as to leave the longest stretch of line between them as is practical. When the length of available main line is longer, for instance about thirty-five feet, it is still desirable to place the feed points well upstream and the pH monitoring point well downstream for optimal pH stabilization.

The method of the present invention preferably uses the system of the present invention. The method of the present invention is a method of continuous fertigation of an agricultural field. This method is practiced or implemented only for an active irrigation system having flowing irrigation water upstream of the agricultural field. In broad embodiments of the present invention, the method comprises the steps of: (step 1) continuous charging a potassium-nutrient feedstock comprised of a plurality of potassium-nutrient-feedstock raw materials to the active agricultural irrigation system by continuously and simultaneously charging a first and a second potassium-nutrient-feedstock raw material to a stream of flowing irrigation water upstream of the agricultural field separately at a first and a second feed point. The first and second potassium-nutrient-feedstock raw materials are selected from the group consisting of potassium hydroxide and a mineral acid selected from the group consisting of nitric acid, phosphoric acid, sulfuric acid and combinations thereof. The first and second feed points are sufficiently proximate each other and the stream of flowing irrigation water has sufficient flow to intermix the first and second potassium-nutrient-feedstock raw materials with each other and with the irrigation water, generating dissolution and reaction exotherms. In preferred embodiments, the raw materials are fed at rates sufficient to provide a concentration of from 1 to 200 ppm of potassium as K2O in said irrigation water, and more preferably 5 to 100 ppm same basis, whereby said irrigation water is converted to treated irrigation water The stream of flowing irrigation water has sufficient flow to dampen the dissolution and reaction exotherms(s). The irrigation water is converted to treated irrigation water. Then (step 2) the agricultural field is irrigated with the treated irrigation water. In preferred embodiments, the flow of the stream of flowing irrigation water is sufficient to dampen the dissolution and reaction exotherms to a maximum temperature increase of 40 degrees F. over ambient irrigation water temperature, and more preferably 20 degrees F. over ambient irrigation water temperature. In various preferred embodiments the method includes charging the first and second potassium-nutrient-feedstock raw materials to a high-dilution environment, such as charging of the potassium-nutrient-feedstock raw materials to the main line and charging to a side-arm mixing chamber that discharges to the main line.

In preferred embodiments of the method of the present invention, the potassium-nutrient-feedstock raw materials are selected from the group consisting of concentrated potassium hydroxide (a 30 to 50 weight percent aqueous solution of potassium hydroxide, and more preferably 40 to 50 wt. percent same basis) and a concentrated mineral acid selected from the group consisting of concentrated nitric acid (a 30 to 68 weight percent aqueous solution of nitric acid, and more preferably 45 to 68 wt. percent same basis), concentrated phosphoric acid (a 50 to 85 weight percent aqueous solution of phosphoric acid, and more preferably 65 to 85 wt. percent same basis), concentrated sulfuric acid (a 50 to 98 weight percent solution of sulfuric acid, and more preferably 80 to 98 wt. percent same basis) and combinations thereof. The plurality of potassium-nutrient-feedstock raw materials being charged may comprise two or more than two potassium-nutrient-feedstock raw materials, and the number and selection of the potassium-nutrient-feedstock raw materials may be changed or altered during the practice of the method of the present invention.

In other embodiments and preferred embodiments, the method further includes the steps of selecting a target pH, determining the pH of the treated irrigation water, and charging an acid, or when necessary, a base, to the stream of flowing irrigation water in an amount sufficient to adjust the pH of the treated irrigation water to a target pH.

While the foregoing written description of the invention enables one of ordinary skill in the art to make and use the invention, and to make and use what is presently considered the best mode of the invention, those of ordinary skill in the art will understand and appreciate the existence of variations, combinations and equivalents of the specific embodiments, methods and examples provided herein. The present invention should not be limited by the above described embodiments, methods and examples. 

We claim:
 1. A system for continuous fertigation of an agricultural field under the irrigation of an active agricultural irrigation system, wherein said system includes continuously charging a potassium-nutrient feedstock to said active agricultural irrigation system, said active agricultural irrigation system having flowing irrigation water upstream of said agricultural field, wherein said potassium-nutrient feedstock is comprised of a plurality of potassium-nutrient-feedstock raw materials, wherein said plurality of potassium-nutrient-feedstock raw materials generate an exotherm upon intermixing with each other and said irrigation water, said system comprising: a plurality of feed points open to a stream of said flowing irrigation water, wherein said stream of said flowing irrigation water has sufficient flow to intermix said plurality of potassium-nutrient-feedstock raw materials with each other and said stream of said flowing irrigation water, generating dissolution and reaction exotherms, when said plurality of potassium-nutrient-feedstock raw materials are simultaneously and separately fed through said plurality of feed points, and wherein said stream of said irrigation water has sufficient flow to dampen said dissolution and reaction exotherms; and means for feeding said plurality of potassium-nutrient-feedstock raw materials simultaneously and separately through said plurality of feed points to said stream of said flowing irrigation water whereby treated irrigation water is formed, and means for irrigating said agricultural field with said treated irrigation water.
 2. The system for continuous fertigation of an agricultural field according to claim 1 wherein said plurality of potassium-nutrient raw-material feed points open to a high-dilution environment.
 3. The system for continuous fertigation of an agricultural field according to claim 1 wherein said active agricultural irrigation system includes a main line, said stream of said flowing irrigation water is flowing through said main line upstream of said agricultural field, and plurality of feed points is disposed along said main line.
 4. The system for continuous fertigation of an agricultural field according to claim 1 wherein said active agricultural irrigation system includes a main line and a side-arm mixing chamber off said main line, and said stream of said irrigation water is flowing through said side-arm mixing chamber and discharging to said main line, and said plurality of feed points are disposed along said side-arm mixing chamber.
 5. The system for continuous fertigation of an agricultural field according to claim 1 further including means to regulate the feed of said plurality of potassium-nutrient-feedstock raw materials being fed to said stream of said flowing irrigation water through said plurality of feed points, including means to commence said feed upon said stream reaching a first pre-selected degree of flow, means to halt said feed upon said stream reaching a second pre-selected degree of flow, and means to separately provide pre-selected degrees of feed through said plurality of feed points.
 6. The system for continuous fertigation of an agricultural field according to claim 1 wherein said active agricultural irrigation system further including means to determine and adjust the pH of said treated irrigation water upstream of said agricultural field.
 7. The system for continuous fertigation of an agricultural field according to claim 1 further including a plurality of storage tanks and a plurality of feed lines, each feed line separately running between a storage tank and a feed point of said plurality of feed points.
 8. The system for continuous fertigation of an agricultural field according to claim 7 wherein said plurality of feed points are spaced apart a maximum of ten inches.
 9. A method of continuous fertigation of an agricultural field, said agricultural field being irrigated by means of an active irrigation system having flowing irrigation water upstream of said agricultural field, said method comprising the steps of: (step 1) continuously charging a potassium-nutrient feedstock comprised of a plurality of potassium-nutrient-feedstock raw materials to said active agricultural irrigation system by continuously charging said plurality of potassium-nutrient-feedstock raw materials to a stream of said flowing irrigation water upstream of said agricultural field simultaneously and separately through a said plurality of feed points; wherein said plurality of potassium-nutrient-feedstock raw materials comprises concentrated potassium hydroxide and a mineral acid selected from the group consisting of concentrated nitric acid, concentrated phosphoric acid, concentrated sulfuric acid, and combinations thereof, wherein said stream of flowing irrigation water has sufficient flow to intermix said plurality of potassium-nutrient-feedstock raw materials with each other and said irrigation water, generating dissolution and reaction exotherms, wherein said stream of flowing irrigation water has sufficient flow to dampen said dissolution and reaction exotherms, whereby said irrigation water is converted to treated irrigation water; and (step 2) irrigating said agricultural field with said treated irrigation water.
 10. The method of continuous fertigation of an agricultural field according to claim 9 wherein said flow of said stream of flowing irrigation water is sufficient to dampen said dissolution and reaction exotherms to a maximum temperature increase of 40 degrees F. over ambient irrigation water temperature.
 11. The method of continuous fertigation of an agricultural field according to claim 9 wherein said flow of said stream of flowing irrigation water is sufficient to dampen said dissolution and reaction exotherms to a maximum temperature increase of 20 degrees F. over ambient irrigation water temperature.
 12. A method of continuous fertigation of an agricultural field under the irrigation of an active agricultural irrigation system, including feeding a potassium-nutrient feedstock to said active agricultural irrigation system, using the fertigation system according to claim 1, said active agricultural irrigation system having flowing irrigation water upstream of said agricultural field, said fertigation system having a plurality of feed points open to a stream of said flowing irrigation water, wherein said plurality of feed points are sufficiently proximate each other and wherein said stream of said irrigation water has sufficient flow to intermix said plurality of potassium-nutrient-feedstock raw materials with each other and with said stream of said flowing irrigation water upon simultaneous and separate charging to said stream of said irrigation water through said feed points, generating dissolution and reaction exotherms, and wherein said stream of flowing irrigation water has sufficient flow to dampen said dissolution and reaction exotherms, and means for separately and simultaneously feeding said plurality of potassium-nutrient-feedstock raw materials through said feed points to said stream of said flowing irrigation water whereby treated irrigation water is formed, wherein said agricultural irrigation system includes means for irrigating said agricultural field with said treated irrigation water, said method comprising the steps of: (step 1) continuously, simultaneously and separately feeding said plurality of potassium-nutrient-feedstock raw materials through said feed points to said stream of flowing irrigation water at levels sufficient to provide a concentration of from 1 to 200 ppm of potassium as K2O in said irrigation water, whereby said irrigation water is converted to treated irrigation water, wherein said plurality of potassium-nutrient-feedstock raw materials comprises concentrated potassium hydroxide and a mineral acid selected from the group consisting of concentrated nitric acid, concentrated phosphoric acid, concentrated sulfuric acid and combinations thereof; and (step 2) irrigating said agricultural field with said treated irrigation water.
 13. The method of continuous fertigation of an agricultural field according to claim 12 wherein said active agricultural irrigation system includes a main line, said stream of said flowing irrigation water is flowing through said main line upstream of said agricultural field, said plurality of feed points are disposed along said main line, and wherein, in said step 1, said continuous, simultaneous and separate feeding said plurality of potassium-nutrient-feedstock raw materials to said stream of flowing irrigation water is feeding to said main line continuously throughout a crop cycle.
 14. The method of continuous fertigation of an agricultural field according to claim 12 wherein said active agricultural irrigation system includes a main line and a side-arm mixing chamber off said main line, and said stream of flowing irrigation water is flowing through said side-arm mixing chamber and discharging to said main line, said plurality of feed points are disposed along said side-arm mixing chamber, and wherein, in said step 1, said continuous, simultaneous and separate feeding said plurality of potassium-nutrient-feedstock raw materials to said stream of flowing irrigation water is feeding to said side-arm mixing chamber continuously throughout a crop cycle.
 15. The method of continuous fertigation of an agricultural field according to claim 12 further including the steps of determining and adjusting the pH of said treated irrigation water upstream of said agricultural field.
 16. The method of continuous fertigation of an agricultural field according to claim 12, wherein said concentrated potassium hydroxide is an aqueous solution containing from 40 to 50 wt. percent potassium hydroxide, said concentrated nitric acid is an aqueous solution containing from 45 to 68 wt. percent nitric acid, said concentrated phosphoric acid is an aqueous solution containing from 65 to 85 wt. percent phosphoric acid and said sulfuric acid is an aqueous solution containing from 80 to 98 wt. percent sulfuric acid.
 17. The method of continuous fertigation of an agricultural field according to claim 12 wherein said flow of said stream of flowing irrigation water is sufficient to dampen said dissolution and reaction exotherms to a maximum temperature increase of 40 degrees F. over ambient irrigation water temperature.
 18. The method of continuous fertigation of an agricultural field according to claim 12 wherein said flow of said stream of flowing irrigation water is sufficient to dampen said dissolution and reaction exotherms to a maximum temperature increase of 20 degrees F. over ambient irrigation water temperature.
 19. The method of continuous fertigation of an agricultural field according to claim 12 wherein said feed points are spaced apart a maximum of ten inches.
 20. The method of continuous fertigation of an agricultural field according to claim 12, wherein, in step 1, said plurality of potassium-nutrient-feedstock raw materials are fed through said feed points to said stream of flowing irrigation water at levels sufficient to provide a concentration of from 5 to 100 ppm of potassium as K2O in said irrigation water. 